Nox排放量。 The cylinder pressure has great influence on the power, economy and emission of a diesel engine. High-speed data collection system was applied to measure cylinder pressure of DI diesel engine, combustion heat release rate has been calculated and analyzed by the cylinder pressure, the model of Nox emission by the measured cylinder pressure of DI diesel engine was established. The model accuracy has been proved by the experiment. The Nox emissions of each cylinder at different speeds and loads have been calculated by the measured cylinder pressure of each cylinder of a multi-cylinder DI diesel engine with this model. The influence of cylinder-to-cylinder variation to Nox emission was analyzed. It is found that if the cylinder pressure is larger, the Nox emission of this cylinder is larger. The Nox emission of the multi-cylinder diesel engine could be reduced when the cylinder-to-cylinder pressure variation reduces.